5.

0 Design of Drain for different Catchmennt areas

Input Data the trapezoid area is: A = by + zy2.

The wetted perimeter is: P = b + 2λ, but by Pythagoras Theorem:
Design intensity of rainfall , I 60 mm/hr λ2 = y2 + (yz)2, or λ = [y2 + (yz)2]1/2, so the wetted perimeter is:
P = b + 2y(1 + z2)1/2, and the hydraulic radius for a trapezoid is:
Run off Coefficient, R 0.6 1
RH = (by + zy2)/[b + 2y(1 + z2)1/2

Trapezoidal
Type of drain drain with 1160 1160 0.01923077
Stone pitching

Manning's Coefficient 0.015

1 2.6 M20+2*(N20*Q20)
Bottom Width 0.6
Side Slope 1.06
θ 0.81 radians
Actual discharge Depth of Depth of Depth of Top Width
NGL @ start NGL @ End Length of Area of Rainfall Cumulative Invert level Invert level Bottom Depth of Angle of Area of Perimeter of Hydraulic Discharge of
from catchment flow at drain at drain at Side Slope Top Width (Excluding Bed slope Manning's Velocity V
drain catchment Intensity Run off coeff. area discharge to drain at start at end Width Start Start flow at End End Side Slope freeboard) flow Flow Radius, R Bed slope 1 in drain Result
Coeff.
Starting End node Mark of
Node Catchment area in m 2
in mm/hr in m /s
3
in m /s
3
in m in m in m in m in m in degress in m in m in m 2
in m 1 in N m/s in m /s
3

in m in m in m in m in m H:V Q < Qcum,

A1 I R Qact = A1 x I x R Qcum = Σ Qact B Df D Df D θ W Wf Af Pf R = Af/Pf N S n V = 1/n R2/3 S 1/2 Q = Af x V
safe

D1 D2 578.3 570.4 300 1 47543 60 0.6 0.475 0.920 577.4 576.800 0.5 0.8 0.9 0.8 0.9 0.28 74.476 1.00 0.944 0.58 2.16 0.27 500 0.0020 0.0145 1.28 0.740 Recheck
1

D3 D2 574.5 570.4 215 2 31695 60 0.6 0.317 0.317 574.1 570.000 0.3 0.3 0.4 0.3 0.4 0.88 48.814 1.00 0.825 0.17 1.10 0.15 52 0.0191 0.0145 2.73 0.461 Safe
2

D4 D5 572 571.2 60 3 15491 60 0.6 0.155 0.155 571.6 570.800 0.3 0.3 0.4 0.3 0.4 0.88 48.814 1.00 0.825 0.17 1.10 0.15 75 0.0133 0.0145 2.29 0.386 Safe
3

D6 D5 573.4 571.1 325 4 51638 60 0.6 0.516 0.516 572.9 570.600 0.3 0.4 0.5 0.4 0.5 0.95 46.469 1.25 1.060 0.27 1.40 0.19 141 0.0071 0.0145 1.94 0.528 Safe
4

D5 D7 571.6 567.6 200 5 36147 60 0.6 0.361 1.033 571.1 567.100 0.3 0.4 0.5 0.4 0.5 1.20 39.806 1.50 1.260 0.31 1.55 0.20 50 0.0200 0.0145 3.35 1.045 Safe
5

D7 D8 569 566.3 190 6 91467 60 0.6 0.915 1.947 568.35 565.650 0.5 0.55 0.65 0.55 0.65 0.96 46.123 1.75 1.558 0.57 2.03 0.28 70 0.0142 0.0145 3.51 1.988 Safe
6

D9 D10 566 563 430 7 92076 60 0.6 0.921 0.921 565.4 562.400 0.4 0.5 0.6 0.5 0.6 0.92 47.490 1.50 1.317 0.43 1.76 0.24 143 0.0070 0.0145 2.25 0.966 Safe
7

D11 D12 566.9 565 185 8 92076 60 0.6 0.921 0.921 566.3 564.400 0.5 0.5 0.6 0.5 0.6 0.83 50.194 1.50 1.333 0.46 1.80 0.25 97 0.0103 0.0145 2.81 1.286 Safe
8

D12 D10 565.7 563.3 285 9 78922 60 0.6 0.789 1.710 565 562.600 0.5 0.6 0.7 0.6 0.7 0.89 48.240 1.75 1.571 0.62 2.11 0.29 119 0.0084 0.0145 2.80 1.742 Safe
9

D14 D13 562.7 560 215 10 228666 60 0.6 2.287 2.287 562 559.300 0.6 0.6 0.7 0.6 0.7 0.82 50.599 1.75 1.586 0.66 2.15 0.30 80 0.0126 0.0145 3.50 2.294 Safe
10

D15 D14 565.5 562.7 265 11 96979 60 0.6 0.970 1.940 564.8 562.000 0.5 0.6 0.7 0.6 0.7 0.89 48.240 1.75 1.571 0.62 2.11 0.29 95 0.0106 0.0145 3.14 1.951 Safe
11

D16 D15 570.7 565.5 305 12 96979 60 0.6 0.970 0.970 570 564.800 0.5 0.6 0.7 0.6 0.7 0.89 48.240 1.75 1.571 0.62 2.11 0.29 59 0.0170 0.0145 3.99 2.478 Safe
12

D17 D18 570.7 565.5 528 13 60 0.6 0.000 1.000 570.1 564.900 0.3 0.5 0.6 0.5 0.6 1.00 45.000 1.50 1.300 0.40 1.71 0.23 102 0.0098 0.0145 2.59 1.038 Safe
13
Total 3503
To Outfall through Culvert from Catchment-8 0.921

Length of Area of Actual discharge Cumulative Invert level Invert level Bottom Depth of Depth of Depth of Depth of Side Slope Top Width Area of Perimeter of Hydraulic Discharge of
NGL @ start NGL @ End from catchment Top Width (Excluding Bed slope Manning's Velocity V
drain catchment area discharge to drain at start at end Width flow drain flow drain freeboard) flow Flow Radius, R Bed slope 1 in drain Result
Coeff.
Starting End node Mark of
Node Catchment area in m 2
in m /s
3
in m /s
3
in m in m in m in m in m in m in m in m 2
in m 1 in N m/s in m /s
3

in m in m in m in m in m V:H Q < Qcum,

A1 Qact = A1 x I x R Qcum = Σ Qact B Df D Df D W Wf Af Pf R = Af/Pf N S n V = 1/n R 2/3
S 1/2 Q = Af x V
safe

D1 D2 527.21 526.71 258 1 15000 0.150 0.150 526.71 525.678 0.5 0.4 0.5 0.4 0.5 1 1.5 1.3 0.360 1.631 0.221 250.000 0.0040 0.025 0.924 0.333 Safe

6.0 Design of Pipe Culvert

Dia of Max Discharge, Percentag Allowable Invert level Invert level

Pipe No of Pipe Length Qmax Depth of flow θ = 2arccos[(r- Area of flow Perimeter Bed slope Hydraulic Bed slope Hydraulic Bed slope Manning's Velocity Discharge, Qallow at start Result
Culvert e of flow K = r2[(θ-sinθ)/2 s=rxθ of Flow 1 in Radius 1 in Radius Coeff. at end
h)/s]
in m in m in m3/s in m in m 1 in N 1 in N N in m/s in m3/s in m in m Qallow < Qmax, safe
Culverts crossing the road -considering maximum discharge from the catchments 1 to 7
0.45 4 5 0.530 75 0.3375 2.094 0.031 0.471 0.13 0.94 250 0.14 250 0.00 0.004 0.012 1.39 0.71 565.65 565.63 safe
Culverts at the outfall of drain
0.5 5 15 0.921 75 0.375 2.094 0.038 0.524 0.16 1.05 400 0.15 400 0.00 0.003 0.012 1.18 0.93 562.4 562.36 safe
Culvert before the ridge - Assumed flow
0.5 3 15 0.300 75 0.375 2.094 0.038 0.524 0.16 1.05 500 0.15 500 0.00 0.002 0.012 1.06 0.50 67.88 67.85 safe
D 0.5
r 0.25
d 0.4
h 0.1

θ 1.85459
K 0.027956
s 0.463648
A 0.168394
pw 1.107149
R 0.152097